spandsp  0.0.6
dtmf.h
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * dtmf.h - DTMF tone generation and detection.
5  *
6  * Written by Steve Underwood <steveu@coppice.org>
7  *
8  * Copyright (C) 2001, 2005 Steve Underwood
9  *
10  * All rights reserved.
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU Lesser General Public License version 2.1,
14  * as published by the Free Software Foundation.
15  *
16  * This program is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19  * GNU Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with this program; if not, write to the Free Software
23  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24  */
25 
26 #if !defined(_SPANDSP_DTMF_H_)
27 #define _SPANDSP_DTMF_H_
28 
29 /*! \page dtmf_rx_page DTMF receiver
30 \section dtmf_rx_page_sec_1 What does it do?
31 The DTMF receiver detects the standard DTMF digits. It is compliant with
32 ITU-T Q.23, ITU-T Q.24, and the local DTMF specifications of most administrations.
33 Its passes the test suites. It also scores *very* well on the standard
34 talk-off tests.
35 
36 The current design uses floating point extensively. It is not tolerant of DC.
37 It is expected that a DC restore stage will be placed before the DTMF detector.
38 Unless the dial tone filter is switched on, the detector has poor tolerance
39 of dial tone. Whether this matter depends on your application. If you are using
40 the detector in an IVR application you will need proper echo cancellation to
41 get good performance in the presence of speech prompts, so dial tone will not
42 exist. If you do need good dial tone tolerance, a dial tone filter can be
43 enabled in the detector.
44 
45 The DTMF receiver's design assumes the channel is free of any DC component.
46 
47 \section dtmf_rx_page_sec_2 How does it work?
48 Like most other DSP based DTMF detector's, this one uses the Goertzel algorithm
49 to look for the DTMF tones. What makes each detector design different is just how
50 that algorithm is used.
51 
52 Basic DTMF specs:
53  - Minimum tone on = 40ms
54  - Minimum tone off = 50ms
55  - Maximum digit rate = 10 per second
56  - Normal twist <= 8dB accepted
57  - Reverse twist <= 4dB accepted
58  - S/N >= 15dB will detect OK
59  - Attenuation <= 26dB will detect OK
60  - Frequency tolerance +- 1.5% will detect, +-3.5% will reject
61 
62 TODO:
63 */
64 
65 /*! \page dtmf_tx_page DTMF tone generation
66 \section dtmf_tx_page_sec_1 What does it do?
67 
68 The DTMF tone generation module provides for the generation of the
69 repertoire of 16 DTMF dual tones.
70 
71 \section dtmf_tx_page_sec_2 How does it work?
72 */
73 
74 #define MAX_DTMF_DIGITS 128
75 
76 typedef void (*digits_rx_callback_t)(void *user_data, const char *digits, int len);
77 
78 /*!
79  DTMF generator state descriptor. This defines the state of a single
80  working instance of a DTMF generator.
81 */
82 typedef struct dtmf_tx_state_s dtmf_tx_state_t;
83 
84 /*!
85  DTMF digit detector descriptor.
86 */
87 typedef struct dtmf_rx_state_s dtmf_rx_state_t;
88 
89 #if defined(__cplusplus)
90 extern "C"
91 {
92 #endif
93 
94 /*! \brief Generate a buffer of DTMF tones.
95  \param s The DTMF generator context.
96  \param amp The buffer for the generated signal.
97  \param max_samples The required number of generated samples.
98  \return The number of samples actually generated. This may be less than
99  max_samples if the input buffer empties. */
100 SPAN_DECLARE(int) dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples);
101 
102 /*! \brief Put a string of digits in a DTMF generator's input buffer.
103  \param s The DTMF generator context.
104  \param digits The string of digits to be added.
105  \param len The length of the string of digits. If negative, the string is
106  assumed to be a NULL terminated string.
107  \return The number of digits actually added. This may be less than the
108  length of the digit string, if the buffer fills up. */
109 SPAN_DECLARE(int) dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len);
110 
111 /*! \brief Change the transmit level for a DTMF tone generator context.
112  \param s The DTMF generator context.
113  \param level The level of the low tone, in dBm0.
114  \param twist The twist, in dB. */
115 SPAN_DECLARE(void) dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist);
116 
117 /*! \brief Change the transmit on and off time for a DTMF tone generator context.
118  \param s The DTMF generator context.
119  \param on-time The on time, in ms.
120  \param off_time The off time, in ms. */
121 SPAN_DECLARE(void) dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time);
122 
123 /*! \brief Initialise a DTMF tone generator context.
124  \param s The DTMF generator context.
125  \return A pointer to the DTMF generator context. */
126 SPAN_DECLARE(dtmf_tx_state_t *) dtmf_tx_init(dtmf_tx_state_t *s);
127 
128 /*! \brief Release a DTMF tone generator context.
129  \param s The DTMF tone generator context.
130  \return 0 for OK, else -1. */
131 SPAN_DECLARE(int) dtmf_tx_release(dtmf_tx_state_t *s);
132 
133 /*! \brief Free a DTMF tone generator context.
134  \param s The DTMF tone generator context.
135  \return 0 for OK, else -1. */
136 SPAN_DECLARE(int) dtmf_tx_free(dtmf_tx_state_t *s);
137 
138 /*! Set a optional realtime callback for a DTMF receiver context. This function
139  is called immediately a confirmed state change occurs in the received DTMF. It
140  is called with the ASCII value for a DTMF tone pair, or zero to indicate no tone
141  is being received.
142  \brief Set a realtime callback for a DTMF receiver context.
143  \param s The DTMF receiver context.
144  \param callback Callback routine used to report the start and end of digits.
145  \param user_data An opaque pointer which is associated with the context,
146  and supplied in callbacks. */
147 SPAN_DECLARE(void) dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s,
148  tone_report_func_t callback,
149  void *user_data);
150 
151 /*! \brief Adjust a DTMF receiver context.
152  \param s The DTMF receiver context.
153  \param filter_dialtone TRUE to enable filtering of dialtone, FALSE
154  to disable, < 0 to leave unchanged.
155  \param twist Acceptable twist, in dB. < 0 to leave unchanged.
156  \param reverse_twist Acceptable reverse twist, in dB. < 0 to leave unchanged.
157  \param threshold The minimum acceptable tone level for detection, in dBm0.
158  <= -99 to leave unchanged. */
159 SPAN_DECLARE(void) dtmf_rx_parms(dtmf_rx_state_t *s,
160  int filter_dialtone,
161  int twist,
162  int reverse_twist,
163  int threshold);
164 
165 /*! Process a block of received DTMF audio samples.
166  \brief Process a block of received DTMF audio samples.
167  \param s The DTMF receiver context.
168  \param amp The audio sample buffer.
169  \param samples The number of samples in the buffer.
170  \return The number of samples unprocessed. */
171 SPAN_DECLARE(int) dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples);
172 
173 /*! Fake processing of a missing block of received DTMF audio samples.
174  (e.g due to packet loss).
175  \brief Fake processing of a missing block of received DTMF audio samples.
176  \param s The DTMF receiver context.
177  \param len The number of samples to fake.
178  \return The number of samples unprocessed. */
179 SPAN_DECLARE(int) dtmf_rx_fillin(dtmf_rx_state_t *s, int samples);
180 
181 /*! Get the status of DTMF detection during processing of the last audio
182  chunk.
183  \brief Get the status of DTMF detection during processing of the last
184  audio chunk.
185  \param s The DTMF receiver context.
186  \return The current digit status. Either 'x' for a "maybe" condition, or the
187  digit being detected. */
188 SPAN_DECLARE(int) dtmf_rx_status(dtmf_rx_state_t *s);
189 
190 /*! \brief Get a string of digits from a DTMF receiver's output buffer.
191  \param s The DTMF receiver context.
192  \param digits The buffer for the received digits.
193  \param max The maximum number of digits to be returned,
194  \return The number of digits actually returned. */
195 SPAN_DECLARE(size_t) dtmf_rx_get(dtmf_rx_state_t *s, char *digits, int max);
196 
197 /*! \brief Get the logging context associated with a DTMF receiver context.
198  \param s The DTMF receiver context.
199  \return A pointer to the logging context */
201 
202 /*! \brief Initialise a DTMF receiver context.
203  \param s The DTMF receiver context.
204  \param callback An optional callback routine, used to report received digits. If
205  no callback routine is set, digits may be collected, using the dtmf_rx_get()
206  function.
207  \param user_data An opaque pointer which is associated with the context,
208  and supplied in callbacks.
209  \return A pointer to the DTMF receiver context. */
210 SPAN_DECLARE(dtmf_rx_state_t *) dtmf_rx_init(dtmf_rx_state_t *s,
211  digits_rx_callback_t callback,
212  void *user_data);
213 
214 /*! \brief Release a DTMF receiver context.
215  \param s The DTMF receiver context.
216  \return 0 for OK, else -1. */
217 SPAN_DECLARE(int) dtmf_rx_release(dtmf_rx_state_t *s);
218 
219 /*! \brief Free a DTMF receiver context.
220  \param s The DTMF receiver context.
221  \return 0 for OK, else -1. */
222 SPAN_DECLARE(int) dtmf_rx_free(dtmf_rx_state_t *s);
223 
224 #if defined(__cplusplus)
225 }
226 #endif
227 
228 #endif
229 /*- End of file ------------------------------------------------------------*/
Definition: private/dtmf.h:50
int filter_dialtone
Definition: private/dtmf.h:61
char digits[MAX_DTMF_DIGITS+1]
Definition: private/dtmf.h:108
Definition: private/dtmf.h:33
int dtmf_rx_free(dtmf_rx_state_t *s)
Free a DTMF receiver context.
Definition: dtmf.c:467
dtmf_tx_state_t * dtmf_tx_init(dtmf_tx_state_t *s)
Initialise a DTMF tone generator context.
Definition: dtmf.c:565
void dtmf_rx_set_realtime_callback(dtmf_rx_state_t *s, tone_report_func_t callback, void *user_data)
Set a realtime callback for a DTMF receiver context.
Definition: dtmf.c:363
float threshold
Definition: private/dtmf.h:85
int dtmf_tx_put(dtmf_tx_state_t *s, const char *digits, int len)
Put a string of digits in a DTMF generator&#39;s input buffer.
Definition: dtmf.c:531
int dtmf_tx(dtmf_tx_state_t *s, int16_t amp[], int max_samples)
Generate a buffer of DTMF tones.
Definition: dtmf.c:501
int dtmf_tx_free(dtmf_tx_state_t *s)
Free a DTMF tone generator context.
Definition: dtmf.c:590
size_t dtmf_rx_get(dtmf_rx_state_t *s, char *buf, int max)
Get a string of digits from a DTMF receiver&#39;s output buffer.
Definition: dtmf.c:348
int dtmf_rx_status(dtmf_rx_state_t *s)
Get the status of DTMF detection during processing of the last audio chunk.
Definition: dtmf.c:338
void dtmf_tx_set_level(dtmf_tx_state_t *s, int level, int twist)
Change the transmit level for a DTMF tone generator context.
Definition: dtmf.c:551
int dtmf_rx_fillin(dtmf_rx_state_t *s, int samples)
Fake processing of a missing block of received DTMF audio samples.
Definition: dtmf.c:316
int dtmf_rx(dtmf_rx_state_t *s, const int16_t amp[], int samples)
Process a block of received DTMF audio samples.
Definition: dtmf.c:102
dtmf_rx_state_t * dtmf_rx_init(dtmf_rx_state_t *s, digits_rx_callback_t callback, void *user_data)
Initialise a DTMF receiver context.
Definition: dtmf.c:407
float reverse_twist
Definition: private/dtmf.h:83
void dtmf_tx_set_timing(dtmf_tx_state_t *s, int on_time, int off_time)
Change the transmit on and off time for a DTMF tone generator context.
Definition: dtmf.c:558
Definition: private/logging.h:33
void dtmf_rx_parms(dtmf_rx_state_t *s, int filter_dialtone, int twist, int reverse_twist, int threshold)
Adjust a DTMF receiver context.
Definition: dtmf.c:373
int dtmf_tx_release(dtmf_tx_state_t *s)
Release a DTMF tone generator context.
Definition: dtmf.c:584
logging_state_t * dtmf_rx_get_logging_state(dtmf_rx_state_t *s)
Get the logging context associated with a DTMF receiver context.
Definition: dtmf.c:401
int dtmf_rx_release(dtmf_rx_state_t *s)
Release a DTMF receiver context.
Definition: dtmf.c:461